The invention relates to methods and tools for cleaving optical fibers.
Optical fibers are used increasingly frequently in waveguides and in communications systems, generally, wherein light energy is transmitted through very long distances within optical fibers with little or no concomitant energy losses. Devices using optical fibers often must be coupled, and such coupling requires the severance of and the reconnecting thereof of the transmitting fibers, which are made, generally, of glass. Loss of light energy at a coupling is detrimental to most transmissions and is to be avoided.
A junction between light fibers should be as near-perfect as possible; that is, the glass-to-glass interface should abut precisely one fiber to another, to minimize energy losses and signal imperfections at these junctures. To accomplish precise joining, a precision cleaving tool must be employed.
Miles of optical fibers are installed xe2x80x9cin the fieldxe2x80x9d, that is, removed from precision instrumentation. Various cleaving tools have been devised for field use, which provide various degrees of acceptability for the cleaved joint and for ease of operation, which also is of paramount importance in field use. Repeatability and consistency in cleavage are important considerations for any field tool.
It is well known that an optical fiber which is bent and then scribed or nicked will break at the scribe as a result of the variation in tensile stress across the cross-section of the fiber created by the bend. The break will generally be brittle and leave only slight imperfections across the fiber cross-section which can be removed by polishing, to produce an acceptable, virtually imperfection-free surface and subsequent joint.
An example of a known scribe-and-break tool for field use is found in U.S. Pat. No. 5,301,868. That patent discloses a scribe-and-break tool for fracturing the free end of an optical fiber said to be suitable for hand-holdable configurations and field use. The tool has an elongated body and a plunger that actuates a blade for scribing the free end of an optical fiber retained in tension within a depressible head that extends outwardly from the body. The free end of the optical fiber contacts the blade, thereby scribing the free end of the fiber causing the free end to break off.
See also the patents referred to and distinguished in U.S. Pat. No. 5,301,868; especially U.S. Pat. No. 5,063,672 which discloses an alternative hand held tool for scoring and severing an optical fiber and is said to be suitable for field use.
A device for cleaving optical fibers is provided. The device includes a housing assembly having an opening therein for receiving an optical fiber to be cleaved, and housing bending and cutting means which are reciprocally moveable in a direction transversely and substantially perpendicularly to the longitudinal axis of an optical fiber inserted into and through the opening into the housing. The housing assembly optionally has a removably connected receptacle for receiving the cut ends of a plurality of cleaved fibers. Upon insertion of an optical fiber through the opening and into the housing, and upon actuation of the bending and cutting means, the fiber is sequentially bent and cleaved and the cut free end is collected in the receptacle.
In operation, preferably the fiber is sheathed within an insulating ceramic ferrule such that the fiber extends outwardly from the ferrule exposing a free end thereof, and the opening in the housing has a diameter large enough to receive the ferrule. The housing includes therein positioning means disposed in close proximity to the opening, which positioning means prevent the fiber/ferrule assembly from insertion into the housing beyond the positioning means, with the sequential bending and cutting means located within the housing so as to provide bending and cutting leaving a predetermined, exposed short length of fiber extending beyond the ferrule after the cutting.
The positioning means may be a stop extending partially over the opening in the housing providing a shoulder within the housing upon which the ferrule rests. The shoulder is positioned at a predetermined depth externally from the opening and internally into the housing, beyond which shoulder the ferrule is prevented from further insertion.
Preferably the cleaving device has sequential bending and cutting means including a boot-shaped pushing head mechanism having an apex or toe and having affixed thereto a cutter, the pushing head being operable to move reciprocally within the housing and adjacent the opening in the direction transversely and substantially perpendicularly to a fiber inserted into and through the opening. The boot toe and cutter are positioned apart from one another along the fiber axis such that, upon movement of the boot toward the fiber, the toe pushes upon and bends the fiber in advance of the cutter contacting and cutting the fiber. The cutter is affixed to the boot such that the cutter contacts and cuts the fiber at a predetermined depth externally from the opening into the housing.
The cutting means is preferably a diamond knife.
The pushing head mechanism is operable by means including a spring-loaded plunger and connecting rod affixed thereto, the plunger being reciprocatingly mounted within a cylinder in a side wall of the housing. In field use, the pushing head is manually operable, in its simplest form by the thumb action of an operator pushing upon the plunger.
The housing assembly and receptacle may be fabricated of aluminum or other metal or another suitable material such as a plastic, e.g. a polycarbonate or a nylon. A preferred material is a glass-filled polycarbonate.